Reads the current GUI face selection with labels, millimeter descriptors, roles, and age to resolve phrases like "these faces"; an empty or expired selection is a normal result.
Call first when the person says 'these faces', 'the faces I selected' or 選んだ面. Read the GUI selection, labels, descriptors in mm, roles and age; an empty or expired selection is a normal answer.
| Name | Required | Description | Default |
|---|---|---|---|
| language | No | ja |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely new behavioral content: the fields returned and the important failure semantics that an empty/expired selection is an expected, non-error outcome.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two short sentences, front-loaded with the primary trigger, then return contents, then the empty-selection caveat. Every clause carries information; nothing is padding.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple read-only tool with no output schema, the description adequately discloses what is returned and how to interpret an empty result. The only gap is the unexplained 'language' parameter, which is a minor omission against an otherwise self-sufficient definition.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
There is one optional 'language' enum parameter with 0% schema description coverage, and the description never mentions it or explains whether it localizes labels vs. descriptors. The enum values and default are visible in the schema, so invocation is still possible, but the description adds no meaning here.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb+resource ('Read the GUI selection') and enumerates what comes back: labels, descriptors in mm, roles and age. The trigger phrases make it unmistakable versus the many listing/status siblings in the toolset.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Gives explicit invocation triggers ('Call first when the person says "these faces" … or 選んだ面') plus a note that an empty/expired selection is a normal answer, which pre-empts a wrong retry path. It stops short of naming an alternative fallback tool if the selection is stale, so it is clear context rather than full when/when-not/alternatives coverage.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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